[PATCH] net: stmmac: loongson1: Use dev_err_probe()

[PATCH] net: stmmac: loongson1: Use dev_err_probe()

[Keguang Zhang via B4 Relay]

From: Keguang Zhang <keguang.zhang@gmail.com>

Use dev_err_probe() for the missing match data case to simplify
error handling.

Signed-off-by: Keguang Zhang <keguang.zhang@gmail.com>
---
 drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c
index de9aba756aac..ec34adb63f61 100644
--- a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c
+++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c
@@ -176,10 +176,8 @@ static int ls1x_dwmac_probe(struct platform_device *pdev)
 				     "Unable to find syscon\n");
 
 	data = of_device_get_match_data(&pdev->dev);
-	if (!data) {
-		dev_err(&pdev->dev, "No of match data provided\n");
-		return -EINVAL;
-	}
+	if (!data)
+		return dev_err_probe(&pdev->dev, -EINVAL, "No of match data provided\n");
 
 	dwmac = devm_kzalloc(&pdev->dev, sizeof(*dwmac), GFP_KERNEL);
 	if (!dwmac)

---
base-commit: ec039126b7fac4e3af35ebccaa7c6f9b6875ba81
change-id: 20260602-dwmac-loongson1-5e1b9dfc3c62

Best regards,
-- 
Keguang Zhang <keguang.zhang@gmail.com>

Re: [PATCH] net: stmmac: loongson1: Use dev_err_probe()

[Jacob Keller]

On 6/15/2026 5:24 AM, Keguang Zhang via B4 Relay wrote:
> From: Keguang Zhang <keguang.zhang@gmail.com>
> 
> Use dev_err_probe() for the missing match data case to simplify
> error handling.
> 
> Signed-off-by: Keguang Zhang <keguang.zhang@gmail.com>
> ---

At first I recalled that dev_err_probe does strange things with
-EPROBE_DEFER. From the documentation for dev_err_probe:

>  * @dev: the pointer to the struct device
>  * @err: error value to test
>  * @fmt: printf-style format string
>  * @...: arguments as specified in the format string
>  *
>  * This helper implements common pattern present in probe functions for error
>  * checking: print debug or error message depending if the error value is
>  * -EPROBE_DEFER and propagate error upwards.
>  * In case of -EPROBE_DEFER it sets also defer probe reason, which can be
>  * checked later by reading devices_deferred debugfs attribute.
>  * It replaces the following code sequence::
>  *
>  *      if (err != -EPROBE_DEFER)
>  *              dev_err(dev, ...);
>  *      else
>  *              dev_dbg(dev, ...);
>  *      return err;
>  *
>  * with::
>  *
>  *      return dev_err_probe(dev, err, ...);
>  *
>  * Using this helper in your probe function is totally fine even if @err
>  * is known to never be -EPROBE_DEFER.
>  * The benefit compared to a normal dev_err() is the standardized format
>  * of the error code, which is emitted symbolically (i.e. you get "EAGAIN"
>  * instead of "-35"), and having the error code returned allows more
>  * compact error paths.
>  *
>  * Returns @err.
>  */

I guess even without -EPROBE_DEFER this is still acceptable. The change
seems fine, if a bit of a minor cleanup. However, net-next is closed,
and this is definitely not a bug-fix worthy of net. This does have the
added benefit of

I'd probably also argue this may go against the desired goals of
net-next with only wanting such cleanups when in the context of other
larger work. Of course that decision ultimately belongs to the maintainers.

You can add my reviewed-by when/if you resubmit when net-next re-opens:

Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>

>  drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c
> index de9aba756aac..ec34adb63f61 100644
> --- a/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c
> +++ b/drivers/net/ethernet/stmicro/stmmac/dwmac-loongson1.c
> @@ -176,10 +176,8 @@ static int ls1x_dwmac_probe(struct platform_device *pdev)
>  				     "Unable to find syscon\n");
>  
>  	data = of_device_get_match_data(&pdev->dev);
> -	if (!data) {
> -		dev_err(&pdev->dev, "No of match data provided\n");
> -		return -EINVAL;
> -	}
> +	if (!data)
> +		return dev_err_probe(&pdev->dev, -EINVAL, "No of match data provided\n");
>  
>  	dwmac = devm_kzalloc(&pdev->dev, sizeof(*dwmac), GFP_KERNEL);
>  	if (!dwmac)
> 
> ---
> base-commit: ec039126b7fac4e3af35ebccaa7c6f9b6875ba81
> change-id: 20260602-dwmac-loongson1-5e1b9dfc3c62
> 
> Best regards,

Re: [PATCH] net: stmmac: loongson1: Use dev_err_probe()

[Jakub Kicinski]

On Tue, 16 Jun 2026 16:42:18 -0700 Jacob Keller wrote:
> I'd probably also argue this may go against the desired goals of
> net-next with only wanting such cleanups when in the context of other
> larger work. Of course that decision ultimately belongs to the maintainers.

Yes, feeding const EINVAL into dev_err_probe() is pretty pointless
so if this helps it's just by "saving" 2 LoC. I'm not sure it's worth
it even in context of larger work, let along by itself.
-- 
pw-bot: reject

Re: [PATCH] net: stmmac: loongson1: Use dev_err_probe()

[Jacob Keller]

On 6/17/2026 1:54 PM, Jakub Kicinski wrote:
> On Tue, 16 Jun 2026 16:42:18 -0700 Jacob Keller wrote:
>> I'd probably also argue this may go against the desired goals of
>> net-next with only wanting such cleanups when in the context of other
>> larger work. Of course that decision ultimately belongs to the maintainers.
> 
> Yes, feeding const EINVAL into dev_err_probe() is pretty pointless
> so if this helps it's just by "saving" 2 LoC. I'm not sure it's worth
> it even in context of larger work, let along by itself.

It does claim that it has benefit since you get the error code emitted
symbolically. But we have %pe for that. I wonder if dev_err_probe
predates %pe?

Per commit: 532888a59505 ("driver core: Better advertise dev_err_probe()"):

>     Describing the usage of dev_err_probe() as being (only?) "deemed
>     acceptable" has a bad connotation. In fact dev_err_probe() fulfills
>     three tasks:
> 
>      - handling of EPROBE_DEFER (even more than degrading to dev_dbg())
>      - symbolic output of the error code
>      - return err for compact error code paths

This was in 2023.. %pe was introduced in 2019, so I guess %pe is even older.

I personally find dev_err_probe acceptable and might find it nice when
writing new code, but I agree its not really meaningful gain to refactor
existing legacy code.

Anyways, all this to say in too many words: this patch doesn't seem to
have much value for netdev.

Thanks,
Jake

Re: [PATCH] net: stmmac: loongson1: Use dev_err_probe()

[Jakub Kicinski]

On Wed, 17 Jun 2026 14:26:25 -0700 Jacob Keller wrote:
> It does claim that it has benefit since you get the error code emitted
> symbolically. But we have %pe for that. I wonder if dev_err_probe
> predates %pe?

I'd argue

  No of match data provided: -EINVAL

is more confusing than just:

  No of match data provided

the EINVAL is meaningless and hardcoded in this case?